AMP is a worse company in almost every single way. Employees hated working there (glassdoor reviews). It's got no moat. Who even used / heard or someone buying an AMP product? Whereas everyone uses either AGL or Energy Australia. Totally different sector.
Whether AMP is a worse or better company in every single way than AGL is a truth or fiction that is yet to play out, however it's an unattractive and unproductive way to be thinking about investing. What is truth and has been for many years is that there is plenty of smart money and mum and dad investors that aren't willing to find out whether it is a worse or better company. The lowest share price for nearly 19 years is proof of that.